תוכן
תמונות
הוסף תמונה שלך
DSS Images Other Images
מאמרים קשורים
Revealing the sub-AU asymmetries of the inner dust rim in the disk around the Herbig Ae star R Coronae Austrinae
Context: Unveiling the structure of the disks around intermediate-masspre-main-sequence stars (Herbig Ae/Be stars) is essential for ourunderstanding of the star and planet formation process. In particular,models predict that in the innermost AU around the star, the dust diskforms a “puffed-up” inner rim, which should result in astrongly asymmetric brightness distribution for disks seen underintermediate inclination. Aims: Our aim is to constrain the sub-AUgeometry of the inner disk around the Herbig Ae star R CrA and searchfor the predicted asymmetries. Methods: Using the VLTI/AMBERlong-baseline interferometer, we obtained 24 near-infrared (H- andK-band) spectro-interferometric observations on R CrA. Observing withthree telescopes in a linear array configuration, each data set samplesthree equally spaced points in the visibility function, providing directinformation about the radial intensity profile. In addition, theobservations cover a wide position angle range (~97°), also probingthe position angle dependence of the source brightness distribution. Results: In the derived visibility function, we detect the signaturesof an extended (Gaussian FWHM ~ 25 mas) and a compact component(Gaussian FWHM ~ 5.8 mas), with the compact component contributing abouttwo-thirds of the total flux (both in H- and K-band). The brightnessdistribution is highly asymmetric, as indicated by the strong closurephases (up to ~40°) and the detected position angle dependence ofthe visibilities and closure phases. To interpret these asymmetries, weemploy various geometric as well as physical models, including a binarymodel, a skewed ring model, and a puffed-up inner rim model with avertical or curved rim shape. For the binary and vertical rim model, noacceptable fits could be obtained. On the other hand, the skewed ringmodel and the curved puffed-up inner rim model allow us tosimultaneously reproduce the measured visibilities and closure phases.From these models we derive the location of the dust sublimation radius(~0.4 AU), the disk inclination angle (~35°), and a north-south diskorientation (PA ~ 180-190°). Our curved puffed-up rim model canreproduce reasonably well the interferometric observables and the SEDand suggests a luminosity of ~29 Lȯ and the presence ofrelatively large (⪆1.2 μm) Silicate dust grains. Our study alsoreveals discrepancies between the measured interferometric observablesand the puffed-up inner rim models, providing important constraints forfuture refinements of these theoretical models. Perpendicular to thedisk, two bow shock-like structures appear in the associated reflectionnebula NGC 6729, suggesting that the detected sub-AU size disk is thedriving engine of a large-scale outflow. Conclusions: Detecting,for the first time, strong non-localized asymmetries in the innerregions of a Herbig Ae disk, our study supports the existence of apuffed-up inner rim in YSO disks.Based on observations made with ESO telescopes at the La Silla ParanalObservatory under programme IDs 079.D-0370(A), 081.C-0272(A,B,C), and081.C-0321(A).
| A catalog of bright calibrator stars for 200-m baseline near-infrared stellar interferometry
We present in this paper a catalog of reference stars suitable forcalibrating infrared interferometric observations. In the K band,visibilities can be calibrated with a precision of 1% on baselines up to200 meters for the whole sky, and up to 300 meters for some part of thesky. This work, extending to longer baselines a previous catalogcompiled by Bordé et al. (2002, A&A, 393, 183), isparticularl y well adapted to hectometric-class interferometers such asthe Very Large Telescope Interferometer (VLTI, Glindemann et al. 2003,Proc. SPIE, 4838, 89) or the CHARA array (ten Brummelaar et al. 2003,Proc. SPIE, 4838, 69) when one is observing well-resolved, high-surfacebrightness objects (K 8). We use the absolute spectro-photometriccalibration method introduced by Cohen et al. (1999, AJ, 117, 1864) toderive the angular diameters of our new set of 948 G8-M0 calibratorstars extracted from the IRAS, 2MASS and MSX catalogs. Angular stellardiameters range from 0.6 mas to 1.8 mas (median is 1.1 mas) with amedian precision of 1.35%. For both the northern and southernhemispheres, the closest calibrator star is always less than 10°away.
| CHARM2: An updated Catalog of High Angular Resolution Measurements
We present an update of the Catalog of High Angular ResolutionMeasurements (CHARM, Richichi & Percheron \cite{CHARM}, A&A,386, 492), which includes results available until July 2004. CHARM2 is acompilation of direct measurements by high angular resolution methods,as well as indirect estimates of stellar diameters. Its main goal is toprovide a reference list of sources which can be used for calibrationand verification observations with long-baseline optical and near-IRinterferometers. Single and binary stars are included, as are complexobjects from circumstellar shells to extragalactic sources. The presentupdate provides an increase of almost a factor of two over the previousedition. Additionally, it includes several corrections and improvements,as well as a cross-check with the valuable public release observationsof the ESO Very Large Telescope Interferometer (VLTI). A total of 8231entries for 3238 unique sources are now present in CHARM2. Thisrepresents an increase of a factor of 3.4 and 2.0, respectively, overthe contents of the previous version of CHARM.The catalog is only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/431/773
| Dynamical Evidence for a Black Hole in the Microquasar XTE J1550-564
Optical spectroscopic observations of the companion star (type G8 IV toK4 III) in the microquasar system XTE J1550-564 reveal a radial velocitycurve with a best-fitting spectroscopic period ofPsp=1.552+/-0.010 days and a semiamplitude ofK2=349+/-12 km s-1. The optical mass function isf(M)=6.86+/-0.71Msolar (1 σ). We tentatively measurethe rotational velocity of the companion star to beVrotsini=90+/-10 km s-1, which when taken at facevalue implies a mass ratio ofQ≡M1/M2=6.6+2.5-1.6 (1σ), using the above value of K2. We derive constraintson the binary parameters from simultaneous modeling of the ellipsoidallight and radial velocity curves. We find 1 σ ranges for thephotometric period (1.5430days<=Pph<=1.5440days),K-velocity (350.2<=K2<=368.6 km s-1),inclination (67.0d<=i<=77.4d), mass ratio (Q>=12.0), andorbital separation(11.55Rsolar<=a<=12.50Rsolar). Given thesegeometrical constraints, we find that the most likely value of the massof the compact object is 9.41 Msolar with a 1 σ rangeof 8.36Msolar<=M1<=10.76Msolar.If we apply our tentative value of Vrotsini=90+/-10 kms-1 as an additional constraint in the ellipsoidal modeling,we find 1 σ ranges of 1.5432days<=Pph<=1.5441daysfor the photometric period, 352.2<=K2<=370.1 kms-1 for the K-velocity, 70.8d<=i<=75.4d for theinclination, 6.7<=Q<=11.0 for the mass ratio, and12.35Rsolar<=a<=13.22Rsolar for the orbitalseparation. These geometrical constraints imply the most likely value ofthe mass of the compact object of 10.56 Msolar with a 1σ range of9.68Msolar<=M1<=11.58Msolar. Ineither case the mass of the compact object is well above the maximummass of a stable neutron star, and we therefore conclude that XTEJ1550-564 contains a black hole. Based on observations collected at theEuropean Southern Observatory, Chile (program 67.D-0229), at theMagellan Walter Baade Telescope at the Las Campanas Observatory, Chile,and the William Herschel Telescope operated on the island of La Palma bythe Isaac Newton Group in the Spanish Observatorio del Roque de losMuchachos of the Instituto de Astrofisica de Canarias.
| Sixth Catalogue of Fundamental Stars (FK6). Part III. Additional fundamental stars with direct solutions
The FK6 is a suitable combination of the results of the HIPPARCOSastrometry satellite with ground-based data, measured over a longinterval of time and summarized mainly in the FK5. Part III of the FK6(abbreviated FK6(III)) contains additional fundamental stars with directsolutions. Such direct solutions are appropriate for single stars or forobjects which can be treated like single stars. Part III of the FK6contains in total 3272 stars. Their ground-based data stem from thebright extension of the FK5 (735 stars), from the catalogue of remainingSup stars (RSup, 732 stars), and from the faint extension of the FK5(1805 stars). From the 3272 stars in Part III, we have selected 1928objects as "astrometrically excellent stars", since their instantaneousproper motions and their mean (time-averaged) ones do not differsignificantly. Hence most of the astrometrically excellent stars arewell-behaving "single-star candidates" with good astrometric data. Thesestars are most suited for high-precision astrometry. On the other hand,354 of the stars in Part III are Δμ binaries in the sense ofWielen et al. (1999). Many of them are newly discovered probablebinaries with no other hitherto known indication of binarity. The FK6gives, besides the classical "single-star mode" solutions (SI mode),other solutions which take into account the fact that hidden astrometricbinaries among "apparently single-stars" introduce sizable "cosmicerrors" into the quasi-instantaneously measured HIPPARCOS proper motionsand positions. The FK6 gives, in addition to the SI mode, the "long-termprediction (LTP) mode" and the "short-term prediction (STP) mode". TheseLTP and STP modes are on average the most precise solutions forapparently single stars, depending on the epoch difference with respectto the HIPPARCOS epoch of about 1991. The typical mean error of anFK6(III) proper motion in the single-star mode is 0.59 mas/year. This isa factor of 1.34 better than the typical HIPPARCOS errors for thesestars of 0.79 mas/year. In the long-term prediction mode, in whichcosmic errors are taken into account, the FK6(III) proper motions have atypical mean error of 0.93 mas/year, which is by a factor of about 2better than the corresponding error for the HIPPARCOS values of 1.83mas/year (cosmic errors included).
| The position corrections of 1400 stars observed with PA II in San Juan.
Not Available
| Fifth fundamental catalogue. Part 2: The FK5 extension - new fundamental stars
The mean positions and proper motions for 3117 new fundamental starsessentially in the magnitude range about 4.5 to 9.5 are given in thisFK5 extension. Mean apparent visual magnitude is 7.2 and is on average2.5 magnitudes fainter then the basic FK5 which has a mean magnitude of4.7. (The basic FK5 gives the mean positions and proper motions for theclassical 1535 fundamental stars). The following are discussed: theobservational material, reduction of observations, star selection, andthe system for the FK5 extension. An explanation and description of thecatalog are given. The catalog of 3117 fundamental stars for the equinoxand epoch J2000.0 and B1950.0 is presented. The parallaxes and radialvelocities for 22 extension stars with large forecasting effects aregiven. Catalogs used in the compilation of the FK5 fundamental catalogare listed.
| UBVRI photometry of FKSZ stars. II
The results of UBVRI photometry for 169 stars of the Faint FundamentalStars Catalog (Zverev, 1957) in the declination zone lambda of between-30 and -60 deg are presented. Observations were obtained between May1984 and February 1987 using the 50-cm ESO telescope at La Silla.Tabular data presented include the number of the star in the E-regions,the V magnitude, the (B-V), (U-B), (V-R), and (R-I) colors, and thespectral types.
|
הכנס מאמר חדש
לינקים קשורים
הכנס לינק חדש
משמש של הקבוצה הבאה
|
תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | קשת |
| התרוממות ימנית: | 19h20m47.32s |
| סירוב: | -38°44'46.8" |
| גודל גלוי: | 7.28 |
| מרחק: | 558.659 פארסק |
| תנועה נכונה: | 15.3 |
| תנועה נכונה: | -16.6 |
| B-T magnitude: | 9.271 |
| V-T magnitude: | 7.445 |
קטלוגים וכינוים:
|
INHABITED SKY
